The invention relates to compositions for the pretreatment of fibers comprising iminodisuccinic acids, their salts and their mixtures with one another, which can have an additional content of citric acid, gluconic acid and/or magnesium in ionic form, for a pretreating bleaching with H.sub.2 O.sub.2. Such compositions are employed in aqueous solution.
Textile-forming natural plant fibers, such as cotton, sisal, jute and the like, and animal fibers, such as silk and wool, comprise, in the crude form, waxes, fats and other plant constituents which cause a yellowish-brown coloring of the fiber. As a result, not all the desired colorations are possible, furthermore, the colorations are not level. A pretreatment in which bleaching and washing are combined is therefore carried out on these fibers to remove the undesirable non-fibrous constituents and to destroy the substances which cause the yellowish-brown coloration. Such a pretreatment can be used on the fibers of the origin mentioned, on yarns produced therefrom and on woven fabric, knitted fabric or nonwovens of such fibers. This pretreatment can furthermore be applied to mixtures of such fibers with synthetic fibers and products produced therefrom.
So-called bleaching liquors which comprise water, hydrogen peroxide, wetting/washing and emulsifying agents, alkali for pH adjustment and H.sub.2 O.sub.2 regulators (bleaching regulators, stabilizers) are employed for carrying out the combined pretreatment mentioned. Water-glass and inorganic phosphates, for example, have been employed as regulators for a long time. When water-glass (Na silicate) is used as a bleaching stabilizer, in particular in combination with Ca salts, insoluble Ca silicate deposits occur on the machine and material. The inorganic phosphates were later replaced by (poly)phosphonate because of over-fertilization of the waste waters. However, these phosphonates, which are regarded as irreplaceable, are difficult to degrade biologically, if at all, and therefore again pollute the waste waters in a different manner. Ethylenediamine-tetraacetic acid (EDTA), which also cannot be degraded biologically and furthermore is not absorbed by sewage sludge, pollutes water and raises objections in its use as an H.sub.2 O.sub.2 regulator. Remobilization of heavy metals by EDTA, moreover, is not completely ruled out.
There was therefore the need to provide completely phosphorus-free and EDTA-free compositions as bleaching regulators (stabilizers), which also cause no deposits brought about, for example, by silicates. Development to date, however, has shown that it did not seem possible to dispense with phosphates or phosphonates or EDTA in such regulators.